VW Beetle HVAC Error: Temp Sensor Trouble Signs

I had a very similar issue with my 2015 VW Golf TSI. Having some experience with HVAC system repairs, I recognized these symptoms immediately. The temperature sensor calibration was completely off, and the control unit ended up being defective. The workshop diagnosed multiple faults in the HVAC system control module. After replacing the control unit, everything started working perfectly again. The total repair cost was 980€, including diagnostic work and parts. However, before jumping to conclusions about your Beetle, it would help to know: What exact error message appears in the cluster? Does the fan still work at any speed? Are you getting any air flow, just not temperature controlled? Have you noticed any unusual sounds from the cooling system? The vehicle maintenance history could also be relevant here, specifically: When was the last AC service performed? Has the cooling system been checked recently? Are there any other electrical issues? These details would help compare if your issue matches what I experienced. The symptoms sound very similar, but VW models can have different control unit configurations even within the same year range.

Last service was done at 115000km. I ran diagnostics and got fault code P0116. The error message says Engine Control System Malfunction. The fan works on all speeds but no cold air comes through, just ambient temperature. No strange noises from the cooling system that I can detect. My main concern is that the temperature readings are inconsistent, showing both high and low values within minutes. I already checked the coolant level and there are no visible coolant leaks around the engine. The AC worked fine about a week ago before these issues started appearing. Given these symptoms, I am leaning toward the temperature sensor being the issue rather than the entire control unit. Would checking the wiring connections to the sensor be a good first step?

Based on the P0116 code and your description of fluctuating temperature readings, this definitely sounds like the same temperature sensor issue I faced with my Golf. The symptoms match exactly what happened in my case before I got it fixed. The engine cooling temperature sensor is causing false readings, which explains why the AC system stays deactivated. The control unit receives incorrect data and goes into a safe mode to protect the system. In my case, I also initially thought it was just the sensor, and checking the wiring is a smart first step. However, after inspecting the connections, the workshop found that prolonged exposure to incorrect sensor data had damaged the control unit itself. A few technical points about the fault code P0116: Its specifically related to the engine coolant temperature sensor circuit, The varying temperature readings are a classic sign of a failing sensor or damaged wiring, The heat exchanger temperature sensor works with the cooling system to manage engine temperature Given your mileage and the sudden onset of problems, replacing just the sensor might solve it. The sensor itself costs around 60€, significantly less than a full control unit replacement. However, if the control unit has been compromised, you might end up needing both parts replaced like I did. The good news is the fan still works, which suggests the basic HVAC hardware is functional. This further points toward a sensor or control issue rather than a mechanical problem in the cooling system.

Thanks for the detailed information about the fault code and symptoms. After considering your experience and suggestions, I think I will start with checking the wiring connections to the temperature sensor. The fluctuating readings and P0116 code do point strongly toward a sensor issue rather than a full control unit failure. The fact that my AC was working perfectly just a week ago makes me hopeful this might be a simpler fix. If replacing the sensor at 60€ could solve both the temperature gauge inconsistency and the AC problems, that would be ideal. Though I understand I might discover more issues once the initial repair starts, similar to your Golf repair experience. I will get the temperature sensor checked first and have the workshop test the control unit before proceeding with any major repairs. At least now I know what to expect and can make a more informed decision when discussing repair options with the mechanic. Vehicle maintenance really comes down to addressing these issues before they cascade into bigger problems.